The present invention relates to semiconductor wafer manufacturing and more specifically to a water slide for transferring semiconductor wafers from a first location in a manufacturing process to a second location in the manufacturing process.
During semiconductor wafer manufacturing, the wafers being processed are subjected to various processing steps during their manufacture. Oftentimes, these wafers are transported in wafer cassettes. During processing, wafers from the cassettes are unloaded, for example onto a conveyor, which conveys the individual wafers through a wafer processing station where a manufacturing step takes place. Following the processing, the wafers are loaded into a cassette from the conveyor.
In one known approach, wafers are transferred from a conveyor to waiting cassettes utilizing a water slide which, during operation, provides a continuous sheet of water across the entire slide regardless of whether a wafer is present on the slide. The slide is tilted downwardly at an angle relative to horizontal so that water will flow down the slide. The water slide of this known construction has a uniformly flat planar bottom surface. As a wafer enters the top of the slide, it is supported entirely from below by the water sheet so that the undersurface of the wafer, adjacent to the upper surface of the slide, does not come in contact with the slide. Any such contact could scratch or otherwise damage the partially processed wafer. As the wafer travels down the slide, it in effect surfs on the sheet of water with the leading (downwardmost) edge of the wafer being elevated relative to the trailing edge by the water as it travels down the slide. In effect, the downwardmost edge of the wafer rides a crest of a wave that forms as the wafer rests on the sheet of water overlying the water slide and travels from the top to the bottom of the slide.
The continuous sheet of water on such a slide also reduces the possibility of wafers jamming or stopping on the slide where they may be impacted by the next wafer entering the slide from the conveyor.
In water slides known to the inventors, to minimize possible wafer damage and provide a complete sheet of water, substantial quantities of water are caused to flow down the water slide. For example, it is not unusual for these known water slide systems to use one hundred gallons of water per hour or more.
These water intensive systems are disadvantageous because relatively expensive distilled water is typically used in these applications. Moreover, water is becoming a scarcer and more costly resource. Therefore, it would be extremely advantageous to provide a water slide system which reduces water use requirements while still effectively transporting the semiconductor wafers between first and second locations in a semiconductor manufacturing process.